Wrap the tortillas in foil and place them in the oven to warm up while you prepare the rest of the meal. Or, wrap them in a clean, damp kitchen towel and microwave them until warm and pliable right before you're ready to eat.
In a large, heavy-bottomed pot, add about an inch and a half vegetable oil; make sure the pot is deep enough so you have a few inches between the top of the layer of oil and the edge of the pot. Heat over medium-high heat until the oil temperature reaches 375°F To see if it has reached the desired temperature, drop a cube of bread in the oil. If it browns up by the count of 40, it’s good to go. Another way to check is to place the tip of the handle to a wood spoon in the oil, if little bubbles form on the sides, the oil is ready.
While the oil is heating up, prepare the avocado sauce: in a food processor, add avocados, garlic, sour cream, zest and juice of two limes and blend until smooth.
For the batter for the fish, combine the flour, salt, sugar and baking powder together in large bowl. Whisk in the beer, hot sauce and sesame seeds, and stir until the batter is smooth. The batter consistency should be quite thick, so add the beer accordingly.
Season the fish with the coriander, chipotle powder and salt.
Working in batches, drop some of the seasoned fish into the bowl with the batter and coat completely. Using a fork or tongs, gently remove the fish from the batter and carefully place into the hot oil. Cook fish for 4-5 minutes, turning continuously, until golden and crispy all over. Cook them in batches if you need to; you don't want to overcrowd the pot. Remove pieces to a paper towel-lined platter.
While the fish is frying, prepare the cabbage mixture: place a large skillet over high heat with two turns of the pan of vegetable oil, about two tablespoons. Once hot, add the shredded cabbage and sliced onions, and cook for 2-3 minutes, stirring frequently. Season with some salt, pepper and juice of one lime.
Add 2-3 pieces of the fish to a tortilla, then top with the avocado sauce and cabbage salad. Fold it and eat it up!